"He seemed just as normal as always that morning," Simpson said. "I had seen nothing unusual."

Her husband, who has no criminal record, even waved and smiled at his brother-in-law and Carlie's father, James Trent, as the pair went about their day.

"We've lived here next door to each other about 20 something years," Simpson said, telling InsideEdition.com that she and her husband had always helped her brother with Carlie and her 7-year-old sister.

"Their whole life, Carlie and Catie, they've been right there," she said. "He was just their uncle. He played with them. Every now and then he'd get on the trampoline with them and try to jump. He just did goofy stuff."

"He helped me take care of our handicapped son all these years. He was good to Carlie and Catie and seemed to love them," she continued. "They loved him with all their heart."

Questions are all Simpson said she has left. She spends her days tending to her disabled adult son and walking back and forth in her home, hoping that she comes up with an idea that will bring her niece home.

"I just pace the floors and try to think of anything I can to help," she said. "That's all I can keep in my head: 'Where would they be, where would they go?'"

The Tennessee Bureau of Investigation announced it shifted its resources to create a command post in Rogersville and said the U.S. Marshals Service dispatched a similar command post to Hawkins County for more boots on the ground. Investigators searching for the little girl have received more than 1,200 tips from 19 states, but so far there have been no credible sightings.

Investigators released on Tuesday new surveillance footage from a Save-A-Lot store of Carlie and her uncle buying toilet paper, soda and food after he had signed her out of school. The new footage came as Carlie's father also shared a video of his daughter, pictured during a happier time.

"Hey, it's me, Carlie," she giggles into screen as she chews a piece of gum.

"This is my dad's phone. I know you've never saw me before, but this is my dad's phone...He never lets me use his phone!" she says as she laughs again.

A reward for information leading to the safe recovery of Carlie and the arrest of her uncle had reached $15,000 by Wednesday. Investigators said anyone interested in contributing to the reward can call 423-923-9100.

"He needs to bring Carlie home," Simpson told InsideEdition.com. "If he's thinking any common sense, he should realize he's in trouble because he didn't tell anybody he was taking her.

"He has to know we're not just sitting here waiting for her to walk in the door," she continued, saying the entire family desperately wants the bubbly little girl back. "My little niece, she misses her sister, she misses her bad. She won't ride a school bus, because her sister's not on there with her. Her dad is partially still in shock, trying to think of anywhere he can go to find her."

The distraught aunt said she's doing the same, hoping that her smart niece can find a way back to the family.

"If I could talk to her right now, I'd tell Carlie I love her and miss her and she needs to come home," she said. "Come home if you can. She don't need to be with her uncle, she needs to be at home."